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Issue 29, 2017, Issue in Progress
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Synthesis of methylated quercetin analogues for enhancement of radical-scavenging activity

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Abstract

Three quercetin derivatives with enhanced radical-scavenging activity were designed and synthesised. Because the radical-scavenging reaction of quercetin is known to proceed via an electron transfer from quercetin to radicals, producing the corresponding quercetin radical cation intermediate, the introduction of electron-donating groups into the quercetin molecule is expected to enhance its radical-scavenging activity. Thus, methyl groups were introduced into the catechol moiety in the quercetin molecule at either the 2′- or 5′-position, or both. All three quercetin analogues were found to exhibit higher radical-scavenging activity than the parent quercetin. The activity of 5′-methylquercetin is the highest among the three analogues. The optimised structure of 5′-methylquercetin calculated by density functional theory demonstrated a coplanar structure between the 4H-curomen (AC rings) and catechol (B ring) moieties, while dimethylquercetin and 2′-methylquercetin have a twisted structure between the AC and B rings. These results demonstrate that the highest radical-scavenging activity of 5′-methylquercetin is due to the stabilisation of the radical cation intermediate by the electron-donating effect of the methyl group as well as by the planar structure of the molecule.

Graphical abstract: Synthesis of methylated quercetin analogues for enhancement of radical-scavenging activity

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Publication details

The article was received on 24 Feb 2017, accepted on 09 Mar 2017 and first published on 24 Mar 2017


Article type: Paper
DOI: 10.1039/C7RA02329D
Citation: RSC Adv., 2017,7, 17968-17979
  • Open access: Creative Commons BY license
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    Synthesis of methylated quercetin analogues for enhancement of radical-scavenging activity

    K. Imai, I. Nakanishi, K. Ohkubo, Y. Ohba, T. Arai, M. Mizuno, S. Fukuzumi, K. Matsumoto and K. Fukuhara, RSC Adv., 2017, 7, 17968
    DOI: 10.1039/C7RA02329D

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